1. Field of the Invention
The invention relates to a wood planing machine, more particularly to one that permits motor-driven height adjustment of a cutter carriage on the wood planing machine.
2. Description of the Related Art
U.S. Pat. No. 5,771,949 discloses a wood planing machine having a carriage locking mechanism for positioning a cutter carriage at an adjusted height relative to a machine base. However, it is noted that the locking mechanism has a relatively complex construction, and assembly thereof is laborious. Moreover, there is a tendency for the locking mechanism to experience elastic fatigue after a period of use, which can cause undesirable problems, such as loosening and vibration of the cutter carriage during operation of the wood planing machine.
In co-pending U.S. patent application Ser. No. 09/741,553, the applicant disclosed a wood planing machine that includes a base, two pairs of parallel hollow posts, two pairs of parallel screw rods, four sprockets, a chain, a cutter carriage, and four threaded members. The hollow posts extend upright from the opposite sides of the base, and are respectively formed with elongated slots that extend along lengths of the posts. The screw rods are disposed respectively in the posts, and are rotatable about axes defined by the screw rods. Each of the screw rods has a portion that is accessible via the slot in the respective one of the posts. The sprockets are connected respectively to the screw rods, and the chain engages the sprockets so as to synchronize rotations of the screw rods. The cutter carriage carries a motor-driven rotary cutter, and includes a pair of parallel carriage seats mounted movably and respectively on the pairs of the posts. Each carriage seat includes top and bottom plates transverse to and spanning a respective pair of the posts, and two opposite side plates interconnecting the top and bottom plates and formed with openings that are registered with the slots in the posts. The threaded members are mounted respectively on the side plates of the carriage seats. Each threaded member includes a bracket plate mounted on the respective side plate, and a sector-shaped threaded portion projecting from the bracket plate through the opening in the respective side plate to engage threadedly a respective screw rod. As such, when a handle that is coupled to one of the screw rods is operated to rotate the screw rods synchronously, the carriage seats can move simultaneously along the posts, and can be held firmly at a desired height relative to the base upon stopping rotation of the screw rods. Planing of a wooden work piece can be conducted at this time.
It is desirable to improve the wood planing machine of the aforesaid co-pending U.S. patent application to permit motor-driven height adjustment of the cutter carriage for added convenience.
Therefore, the main object of the present invention is to provide a wood planing machine that permits motor-driven height adjustment of a cutter carriage on the wood planing machine.
Another object of the present invention is to provide a wood planing machine that further permits manual height adjustment of the cutter carriage.
According to the present invention, a wood planing machine comprises:
a base having two opposite sides;
two pairs of parallel hollow posts that extend upright from the opposite sides of the base, and that are respectively formed with elongated slots extending along lengths of the posts;
two pairs of parallel screw rods disposed respectively in the posts, and rotatable about axes defined by the screw rods, each of the screw rods having a portion that is accessible via the slot in the respective one of the posts;
four first sprockets connected respectively to the screw rods;
a chain engaging the first sprockets so as to synchronize rotations of the screw rods;
a cutter carriage including first and second carriage seats mounted movably and respectively on the pairs of the posts, each of the carriage seats includes top and bottom plates transverse to and spanning the respective pair of the posts, and two opposite side plates interconnecting the top and bottom plates and formed with openings that are registered with the slots in the posts;
four threaded members mounted respectively on the side plates of the carriage seats, each of the threaded members including a bracket plate mounted on the respective one of the side plates, and a sector-shaped threaded portion projecting from the bracket plate through the opening in the respective one of the side plates to engage threadedly a respective one of the screw rods so as to permit the carriage seats to move simultaneously along the posts when the screw rods rotate synchronously, and to be held firmly at a desired height relative to the base upon stopping rotation of the screw rods;
a drive shaft disposed rotatably on the base parallel to the screw rods and adjacent to the first carriage seat;
a second sprocket connected to the drive shaft and engaging the chain such that rotation of the drive shaft can result in corresponding rotation of the screw rods;
a motor-driven rotary cutter mounted on the cutter carriage and having a rotatable drive axle that extends into the first carriage seat between the top and bottom plates and between the side plates of the first carriage seat;
a drive gear mounted securely and co-axially on the drive axle so as to be rotatable therewith;
a gear mounting seat having upper and lower plate portions and abridging plate portion that interconnects the upper and lower plate portions;
an upper driven gear mounted rotatably on the upper plate portion of the gear mounting seat, and sleeved slidably on and rotatable with the drive shaft; and
a lower driven gear mounted rotatably on the lower plate portion of the gear mounting seat, and sleeved slidably on and rotatable with the drive shaft.
The gear mounting seat is movable along the drive shaft relative to the first carriage seat to a selected one of an intermediate first position, where the upper and lower driven gears disengage the drive gear, an upper second position, where the upper driven gear disengages and the lower driven gear engages the drive gear, and a lower third position, where the lower driven gear disengages and the upper driven gear engages the drive gear.